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Natural Chemicals

In this worksheet, students explore the chemicals in the atmosphere, hydrosphere and the lithosphere. The Year 11 Bonding worksheet contains more information about the different types of bonding and is related to this worksheet.

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QUESTION 1 of 10

The Earth's atmosphere is made of air, which contains water vapour, nitrogen, argon, oxygen and carbon dioxide. Nitrogen makes up 78% of air and oxygen is approximately 21%. The other elements and compounds are in very low percentage. The concentration of water vapour varies from area to area. Most of the elements exist in diatomical (two atoms) molecules, e.g. O2 (oxygen) and N2 (nitrogen). Examples of the compounds are H2O (water) and CO2 (carbon dioxide).

The bonds between those atoms are strong covalent points, but intermolecular forces that link the molecules together are very weak and break easily when the substance melts or boils. The picture below shows a model of the water molecule, where the blue atoms are hydrogen atoms and the red one is the oxygen atom. The lines between them are the covalent bonds between the atoms. They can be single (one line), double (two lines) and triple (three lines) depending on how many pairs of electrons are shared (one line represents the bond between a pair of electrons).

The Earth's hydrosphere is made up of the oceans. They contain ionic compounds - mainly salts - which form when atoms give or take electrons and become positive or negative ions respectively. Common salt, the one we eat, is sodium chloride (see diagram below). When solid, ionic compounds do not conduct electricity, because their ions are held firmly in a fixed position, but when they melt, the ions are free to move, so they are able to conduct electricity. The amount of charge the ions have depends on the number of electrons they have given or taken. For more information on types of bonding, you can see the Bonding worksheet.

The Earth's lithosphere is made of the crust (the outer thin rocky layer) and the upper mantle (the layer of mantle just below the crust). The lithosphere is rich in oxygen, silicon and aluminium compounds. Silicon dioxide (commonly known as silica) has a giant covalent structure and is very hard, with a high melting and boiling point. Sand on the beach is mostly silicon dioxide. The lithosphere is also rich in valuable gemstones, like quartz, amethyst and, of course, diamond. These are very hard and do not corrode, which increases their value.

Which is the most prevalent element in air?

oxygen

carbon dioxide

nitrogen

What is the percentage of oxygen in the air?

20%

23%

21%

What types of bonds mainly exist between atoms of elements and compounds in the atmosphere? Type the word in the box below.

Select the correct option below which completes this sentence:

In covalent substances intermolecular forces that link the molecules together are.......

very weak

very strong

very strong when the substance melts

What would you use to represent a double covalent bond?

a single line

a double line

a triple line

What type of compounds is the Earth's hydrosphere made of?

ionic

covalent

What is the chemical name of common salt? Type the two words in the answer box below.

Do solid ionic compounds conduct electricity?

yes

no

Why do ionic compounds in a liquid state conduct electricity easily?

their electrons are in a fixed position

their electrons open up for electricity to flow through

their electrons are free to move

What type of elements exist in abundance in the lithosphere? Tick three boxes.

oxygen

zinc

aluminium

calcium sulfate

water

silica

ANSWERS

Question 1

Which is the most prevalent element in air?

CORRECT ANSWER

nitrogen

EDDIE SAYS

78% of the air we breath is made up of Nitrogen.

ANSWERS

Question 2

What is the percentage of oxygen in the air?

CORRECT ANSWER

21%

EDDIE SAYS

The air is made of 21% oxygen.

ANSWERS

Question 3

What types of bonds mainly exist between atoms of elements and compounds in the atmosphere? Type the word in the box below.

CORRECT ANSWER

covalent

EDDIE SAYS

Atoms of elements and compounds in the atmosphere are linked by covalent bonds.

ANSWERS

Question 4

Select the correct option below which completes this sentence:

In covalent substances intermolecular forces that link the molecules together are.......

CORRECT ANSWER

very weak

EDDIE SAYS

In covalent substances intermolecular forces that link the molecules together are very weak and break easily when the substance melts or boils.

ANSWERS

Question 5

What would you use to represent a double covalent bond?

CORRECT ANSWER

a double line

EDDIE SAYS

We use a double line between atoms to represent a double covalent bond.

ANSWERS

Question 6

What type of compounds is the Earth's hydrosphere made of?

CORRECT ANSWER

ionic

EDDIE SAYS

The Earth's hydrosphere (the oceans) is made of mainly salts, which are ionic compounds.

ANSWERS

Question 7

What is the chemical name of common salt? Type the two words in the answer box below.

CORRECT ANSWER

sodium chloride

EDDIE SAYS

The chemical name of the the salt we eat is sodium chloride.

ANSWERS

Question 8

Do solid ionic compounds conduct electricity?

CORRECT ANSWER

no

EDDIE SAYS

Solid ionic compounds do not conduct electricity.

ANSWERS

Question 9

Why do ionic compounds in a liquid state conduct electricity easily?

CORRECT ANSWER

their electrons are free to move

EDDIE SAYS

Ionic compounds in a liquid state conduct electricity easily, because their electrons are free to move.

ANSWERS

Question 10

What type of elements exist in abundance in the lithosphere? Tick three boxes.

CORRECT ANSWER

oxygenaluminiumsilica

EDDIE SAYS

Oxygen, silica and aluminium compounds are the most prevalent in the lithosphere.